PROJECT SUMMARY/ABSTRACT Development is highly regular between individuals despite growth in different environments. This maintenance of developmental consistency in different environments is called buffering. In organisms that cannot control their internal body temperature, there are differing rates of development as temperatures change and this requires mechanisms to buffer development. Gene expression and chromatin structure are two related systems that need to be regulated for buffering to be maintained. In this proposal I will investigate the molecular mechanisms that underlie the buffering of larval and germline development in C. elegans. During the mentored phase of this grant I will learn chromatin immunoprecipitation techniques and train in the programming and bioinformatic skills needed to analyze the resulting data. During my postdoc I have established a role for synMuv B transcriptional regulators in suppressing the expression of germline genes in the soma. In these mutants, germline gene misexpression results in high temperature larval arrest. I will use the skills I learn in the mentored phase to study how histone modification patterns on chromatin change in the soma of synMuv B mutants in response to high temperature. I will also study how the levels of chromatin compaction respond to temperature in synMuv B mutants and if there are predictable changes in the location of particular loci within the nuclear space in response to temperature. These studies should lay the foundation of how synMuv B proteins buffer gene expression and larval development at the molecular level in response to temperature and to what extent these mechanisms rely on chromatin structure. Once the independent phase of the grant begins I will extend my studies on the buffering of gene expression and chromatin to the germ line. I plan to examine the synMuv B mutant lin-35, which shows loss of fertility and changes in chromatin structure in developing germ cells at high temperature but not at low temperature. LIN-35 is the sole worm homolog of human retinoblastoma, a tumor suppressor that is mutated in almost all human cancers. By studying the temperature-sensitive defects seen in the soma and germ line of lin-35 mutants, more may be learned about the temperature sensitivity that occurs in cancer cells. During the independent phase I will also expand my studies into new pathways that may play an important role in buffering gene expression and chromatin structure at high temperature. I will study candidates that I obtained from a screen for suppressors of synMuv B high temperature larval arrest to find new pathways in the maintenance of larval development at high temperature. The studies proposed here will expand our knowledge of how organisms respond to changes in the environment and to what extent these responses are mediated though chromatin structure.